Daniels is a very good guide but a lot of recent training philosophy now tends to go beyond that. First of all, very talented son you have if he is already running 9:30. Second, I would focus on a more strength based approach over the winter especially if he is running longer distances. Also important to stay in touch with speed periodically through strides and shorter maximal sprint training. Given it’s a long way until spring and his coach will likely have a heavy focus on speed work during the season, I would recommend something like this.
M-easy run plus short hill sprints to work on maximal speed. Find a steep hill and sprint up for 6-12 seconds. Take 3-5 minutes recovery in between and work up to 6-10 reps.
T- Tempo run or threshold intervals. A traditional Daniels 20-30 minute tempo is a good option but I prefer broken tempos or threshold intervals and is what I usually implement with my athletes. Examples being 8x3 minutes with 1 minute rest, 4x6 minutes minutes with 1 min rest, or 3x8-10 minutes with 2-3 minutes rest. Make sure these are at a threshold effort with a focus on not going too fast. It is better to run these a little slower rather than too fast or you can risk burning out or injury.
Periodically (maybe every other week) add 4x200 at current race pace to the end of these for a bit more speed focus.
W-Easy +strides/cross train
Thu: choose one of the threshold workouts from Tuesday or do a hill session. Find a moderate grade hill and work up to doing 10-12 x1 min or 6-10x2 minutes with a walk down recovery.
F-easy plus strides/cross train
Sat- long run
Sunday- rest or cross train.
Following something along these lines should have him very strong going into the season, and as I mentioned before, the focus of workouts then will transition likely into your more traditional interval sessions on the track.
Good luck to your son and let me know if you have any questions.